Optical sampling method for analog to digital conversion

Abstract

A method and apparatus for encoding data. A first pair of optical signals having a first phase difference is generated in response to receiving an input signal having a voltage. A second pair of optical signals having a second phase difference is generated in response to receiving an input signal having a voltage. The first pair of optical signals is combined to form a first optical signal having a first intensity. The second pair of optical signals is combined to form a second optical signal having a second intensity. The first intensity of the first optical signal reaches a peak at a different time from the second intensity of the second optical signal.

1. An apparatus comprising:
 a modulation system configured to generate a first pair of optical signals having a first phase difference and a second pair of optical signals having a second phase difference in response to an input signal, the input signal is selected from one of a voltage signal, a current signal, a frequency signal, and a charge, wherein the first pair of optical signals are combined to form a first optical signal having a first intensity and the second pair of optical signals are combined to form a second optical signal having a second intensity, and wherein the first intensity of the first optical signal reaches a peak at a different time from the second intensity of the second optical signal; 
 an optical detector system coupled to the modulation system, wherein the optical detector system is configured to generate a first electrical signal corresponding to the first intensity of the first optical signal and a second electrical signal corresponding to the second intensity of the second optical signal; and 
 an analog to digital conversion system connected to the optical detector system, wherein the analog to digital conversion system is configured to generate digital data from the first electrical signal and the second electrical signal. 
 
     
     
       2. The apparatus of  claim 1 , wherein the first intensity of the first optical signal is based on the first phase difference and the second intensity of the second optical signal is based on the second phase difference. 
     
     
       3. The apparatus of  claim 1 , wherein the first pair of optical signals and the second pair of optical signals are combined in a constructive combination or a destructive combination. 
     
     
       4. The apparatus of  claim 1 , wherein the optical detector system comprises:
 a first optical detector coupled to the first optical signal, wherein the first optical detector is configured to generate the first electrical signal corresponding to the first intensity; and 
 a second optical detector coupled to the second optical signal, wherein the second optical detector is configured to generate the second electrical signal corresponding to the second intensity. 
 
     
     
       5. The apparatus of  claim 1 , wherein the modulation system comprises:
 a plurality of interferometers configured to modulate an optical signal to generate the first optical signal and the second optical signal. 
 
     
     
       6. The apparatus of  claim 1 , wherein the first optical signal is substantially proportional to (1+sin(kV)), and the second optical signal is substantially proportional to (1+cos(kV)), and wherein k is a constant and V is voltage. 
     
     
       7. The apparatus of  claim 1  further comprising:
 a light source configured to generate an optical signal used by the modulation system to generate the first optical signal and the second optical signal. 
 
     
     
       8. The apparatus of  claim 1 , wherein the analog to digital conversion system is configured to perform a two-argument inverse tangent operation using the first optical signal and the second optical signal to generate the digital data. 
     
     
       9. The apparatus of  claim 1 , wherein the analog to digital conversion system comprises a processor. 
     
     
       10. The apparatus of  claim 6 , wherein the modulation system is configured to generate a third optical signal having a third intensity substantially proportional to the input signal, wherein the third optical signal is used to recover a phase of modulation. 
     
     
       11. The apparatus of  claim 10 , wherein the phase of modulation is substantially linearly related to the voltage. 
     
     
       12. The apparatus of  claim 10 , wherein the modulation system is configured to generate a fourth optical signal having a fourth intensity and a fifth optical signal having a fifth intensity, wherein the fourth optical signal is substantially proportional to (1−sin(kV)), and the fifth optical signal is substantially proportional to (1−cos(kV)), and wherein the fourth optical signal and the fifth optical signal are used to reduce or eliminate noise. 
     
     
       13. A method for encoding data, the method comprising:
 responsive to receiving an input signal having a voltage, generating a first pair of optical signals having a first phase difference, wherein the input signal is selected from one of a voltage signal, a current signal, a frequency signal, and a charge; 
 responsive to receiving the input signal having the voltage, generating a second pair of optical signals having a second phase difference; 
 combining the first pair of optical signals to form a first optical signal having a first intensity; 
 
       combining the second pair of optical signals to form a second optical signal having a second intensity, wherein the first intensity of the first optical signal reaches a peak at a different time from the second intensity of the second optical signal;
 converting the first optical signal into a first electrical signal corresponding to the first intensity; 
 
       converting the second optical signal into a second electrical signal corresponding to the second intensity; and
 generating digital data from the first electrical signal and the second electrical signal. 
 
     
     
       14. The method of  claim 13 , wherein the step of combining the first pair of optical signals to form the first optical signal having the first intensity comprises:
 combining the first pair of optical signals to form the first optical signal having the first intensity, wherein the first intensity of the first optical signal is based on the first phase difference; and 
 wherein the step of combining the second pair of optical signals to form the second optical signal having the second intensity comprises:
 combining the second pair of optical signals to form the second optical signal having the second intensity, wherein the second intensity of the second optical signal is based on the second phase difference. 
 
 
     
     
       15. The method of  claim 13  further comprising:
 generating a third optical signal having a third intensity substantially proportional to the input signal, wherein the third optical signal is used to recover a phase of modulation. 
 
     
     
       16. The method of  claim 13 , wherein the step of generating the digital data from the first electrical signal and the second electrical signal comprises:
 performing a two-argument inverse tangent operation, by an analog to digital conversion system, using the first optical signal and the second optical signal to generate the digital data. 
 
     
     
       17. The method of  claim 13 , wherein the step of combining the first pair of optical signals to form the first optical signal having the first intensity comprises:
 combining the first pair of optical signals to form the first optical signal having the first intensity, wherein the first optical signal is substantially proportional to (1+sin(kV)), and wherein k is a constant and V is an amplitude of the voltage signal; and 
 wherein the step of combining the second pair of optical signals to form the second optical signal having the second intensity comprises:
 combining the second pair of optical signals to form the second optical signal having the second intensity, wherein the second optical signal is substantially proportional to (1+cos(kV)). 
 
 
     
     
       18. The method of  claim 13 , wherein the step of generating the first pair of optical signals having the first phase difference in response to receiving the input signal comprises:
 responsive to receiving the input signal, generating the first pair of optical signals having the first phase difference using a modulation system; and 
 wherein the step of generating the second pair of optical signals having the second phase difference in response to receiving the input signal comprises:
 responsive to receiving the input signal, generating the second pair of optical signals having the second phase difference using the modulation system. 
 
 
     
     
       19. The method of  claim 13 , wherein the step of converting the first optical signal into the first electrical signal corresponding to the first intensity comprises:
 converting the first optical signal into the first electrical signal corresponding to the first intensity using an optical detector system; and 
 wherein the step of converting the second optical signal into the second electrical signal corresponding to the second intensity comprises:
 converting the second optical signal into the second electrical signal corresponding to the second intensity using the optical detector system. 
 
 
     
     
       20. The method of  claim 13 , wherein the step of generating the digital data from the first electrical signal and the second electrical signal further comprises:
 generating the digital data from the first electrical signal and the second electrical signal using an analog to digital conversion system.